DENVER (AP) The Chicago Cubs have put pitcher John Lackey on the 15-day disabled list because of strained right shoulder.
The Cubs made a series of moves Friday before their scheduled game in Colorado.
The 37-year-old Lackey has made 24 starts this year in his first season with the NL Central leaders. He is 9-7 with a 3.41 ERA.
Lackey's move to the DL was retroactive to Monday.
The Cubs also put right-handed reliever Hector Rondon on the 15-day disabled list with a strained right triceps. He is a 2-3 with a team-leading 18 saves and a 2.47 ERA. That move was retroactive to Wednesday.
Right-hander Felix Pena and left-hander Rob Zastryzny had their contracts selected from Triple-A Iowa.
To make room on the 40-man roster for the two additions, right-handers Dallas Beeler and Aaron Brooks were transferred to the 60-day disabled list.
The loss of Lackey and Rondon came when the Cubs had the best record in the majors.
''It makes it easier to maneuver, but you'd still do it any way,'' manager Joe Maddon said. ''If you have guys that need time to get ready, you should give them time to get well. You don't want to push that because on the backside, it can only be a big negative.''
Pena and Zastryzny are both on a major league roster for the first time.
Zastryzny, a second-round pick out of Missouri in 2013, split time between Double-A Tennessee and Iowa, going a combined 10-5 with a 4.31 ERA in 23 starts and a relief outing.
Pena was originally signed by the Cubs in 2009 as an undrafted free agent out of the Dominican Republic. He has gone 3-4 with three saves and a 3.41 ERA at Iowa.
Maddon said he has no qualms about filling the rotation and bullpen vacancies with first-time major leaguers.
''I like it,'' Maddon said. ''Sometimes, you catch lightning in the bottle. You find out. I've been there before with two guys in my history that have really lit it up at the end of the year in Frankie Rodriguez and David Price. You never know. You never know what you are going to catch.''
''We've got to put them out there in the right spots, break them in nice and easily. But again at the end of the day, these are the kind of moments that a guy can really try to poke his career, too,'' he said.